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Lichens are remarkable and classic examples of symbiotic organisms that have fascinated scientists for centuries. Yet, it has only been for a couple of decades that significant advances have focused on the diversity of their green algal and/or cyanobacterial photobionts. Cyanolichens, which contain cyanobacteria as their photosynthetic partner, include up to 10% of all known lichens and, as such, studies on their cyanobionts are much rarer compared to their green algal counterparts. For the unicellular cyanobionts, i.e. cyanobacteria that do not form filaments, these studies are even scarcer. Nonetheless, these currently include at least 10 different genera in the cosmopolitan lichen order Lichinales. An international consortium (International Network of CyanoBionts; INCb) will tackle this lack of knowledge. In this article, we discuss the status of current unicellular cyanobiont research, compare the taxonomic resolution of photobionts from cyanolichens with those of green algal lichens (chlorolichens), and give a roadmap of research on how to recondition the underestimated fraction of symbiotic unicellular cyanobacteria in lichens., Competing Interests: None declared., (© The Author(s) 2024. Published by Oxford University Press on behalf of the International Society for Microbial Ecology.)

The characterization of cyanobacteria communities remains challenging, as taxonomy of several cyanobacterial genera is still unresolved, especially within Nostocales taxa. Nostocales cyanobacteria are capable of nitrogen fixation; nitrogenase genes are grouped into operons and are located in the same genetic locus. Structural nitrogenase genes (nifH, nifK and nifD) as well as 16S rRNA have been shown to be adequate genetic markers for distinguishing cyanobacterial genera. However, there is no available information regarding the phylogeny of regulatory genes of the nitrogenase cluster. Aiming to provide a more accurate overview of the evolution of nitrogen fixation, this study analyzed for the first time nifE and nifN genes, which regulate the production of nitrogenase, alongside nifH. Specific primers were designed to amplify nifE and nifN genes, previously not available in literature and phylogenetic analysis was carried out in 13 and 14 TAU-MAC culture collection strains, respectively, of ten Nostocales genera along with other sequences retrieved from cyanobacteria genomes. Phylogenetic analysis showed that these genes seem to follow a common evolutionary pattern with nitrogenase structural genes and 16S rRNA. The classification of cyanobacteria based on these molecular markers seems to distinguish Nostocales strains with common morphological, ecological, and physiological characteristics., (© The Author(s) 2024. Published by Oxford University Press on behalf of FEMS.)

Cyanobacterial toxins (known as cyanotoxins) disrupt the plant cytoskeleton (i.e. microtubules and F-actin), which is implicated in the regulation of cell wall architecture. Therefore, cyanotoxins are also expected to affect cell wall structure and composition. However, the effects of cyanobacterial toxicity on plant cell wall have not been yet thoroughly studied. Accordingly, the alterations of cell wall matrix after treatments with pure microcystin-LR (MC-LR), or cell extracts of one MC-producing and one non-MC-producing Microcystis strain were studied in differentiated Oryza sativa (rice) root cells. Semi-thin transverse sections of variously treated LR-White-embedded roots underwent immunostaining for various cell wall epitopes, including homogalacturonans (HGs), arabinogalactan-proteins (AGPs), and hemicelluloses. Homogalacturonan and arabinan distribution patterns were altered in the affected roots, while a pectin methylesterase (PME) activity assay revealed that PMEs were also affected. Elevated intracellular Ca 2+ levels, along with increased callose and mixed linkage glucans (MLGs) deposition, were also observed after treatment. Xyloglucans appeared unaffected and lignification was not observed. The exact mechanism of cyanobacterial toxicity against the cell wall is to be further investigated., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Masson SAS. All rights reserved.)

In the large and morphologically diverse phylum of Chlorophyta, new taxa are discovered every year and their phylogenetic relationships are reconstructed by the incorporation of molecular phylogenetic methods into traditional taxonomy. Herein, we aim to contribute to the photosynthetic microorganisms' diversity knowledge in the Mediterranean area, a relatively unexplored ecoregion with high diversity. Based on a polyphasic approach, 18 Chlorophyta isolates were investigated and characterized. Morphological characteristics and ultrastructure, the phylogeny based on 18S rRNA gene (small subunit ribosomal RNA), 18S-28S internal transcribed spacer (ITS region), and the ribulose-1,5-bisphosphate carboxylase/oxygenase large subunit region ( rbcL gene), support establishing four new genera ( Nomia , Ava , Akraea , Lilaea ) and five new species ( Spongiosarcinopsis limneus , N. picochloropsia , Av. limnothalassea , Ak. chliaropsychia , and L. pamvotia ) belonging to orders Sphaeropleales, Chlorellales, and Chlamydomonadales. For some of them, this is the first report of their occurrence in specific aquatic environments.

Well-studied thermal spring microbial mat systems continue to serve as excellent models from which to make discoveries of general importance to microbial community ecology in order to address comprehensively the question of "who is there" in a microbial community. Cyanobacteria are highly adaptable and an integral part of many ecosystems including thermal springs. In this context, we sampled disparate thermal springs, spanning from Iceland and Poland to Greece and Tajikistan. Thirteen (13) strains were isolated and characterised with taxonomic indices and molecular markers (16S-23S rRNA region and cpcBA gene), whilst their thermotolerance was evaluated. Screening for the presence of genes encoding three heat shock proteins, as well as non-ribosomal peptide synthetases (NRPSs) and polyketide synthases (PKSs) was performed. This approach resulted in the description of two new genera (Hillbrichtia and Amphirytos) and their type species (Hillbrichtia pamiria and Amphirytos necridicus) representing Oscillatoriales and Synechococcales orders, respectively. We also found unique lineages inside the genus Thermoleptolyngbya, describing a novel species (T. hindakiae). We described the presence of sub-cosmopolitan taxa (such as Calothrix, Desertifilum, and Trichormus). Strains were diverse concerning their thermophilic ability with the strains well adapted to high temperatures possessing all three investigated genes encoding heat shock proteins as well as studied PKS and NRPS genes. In this work, we show novel cyanobacteria diversity from thermal springs from disparate environments, possible correlation of thermotolerance and their genetic background, which may have implications on strategic focusing of screening programs on underexploited taxa in these habitats., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Urbanization transforms environments in ways that alter biological evolution. We examined whether urban environmental change drives parallel evolution by sampling 110,019 white clover plants from 6169 populations in 160 cities globally. Plants were assayed for a Mendelian antiherbivore defense that also affects tolerance to abiotic stressors. Urban-rural gradients were associated with the evolution of clines in defense in 47% of cities throughout the world. Variation in the strength of clines was explained by environmental changes in drought stress and vegetation cover that varied among cities. Sequencing 2074 genomes from 26 cities revealed that the evolution of urban-rural clines was best explained by adaptive evolution, but the degree of parallel adaptation varied among cities. Our results demonstrate that urbanization leads to adaptation at a global scale.

Cyanobacteria are ecologically versatile microorganisms, occupying diverse habitats, from terrestrial caves to coastal shores and from brackish lakes to thermal springs. Cyanobacteria have also been linked with hydrogen cyanide (HCN), mainly for their ability to catabolize HCN by the nitrogenase enzyme. In this context, we sampled disparate environments, spanning from Canary Islands and Iceland to Estonia and Cyprus. Eighty-one (81) strains were isolated and characterised with taxonomic indices and molecular markers (16S-23S rRNA region and cpcBA region), whilst their ability to produce HCN was evaluated. This approach resulted in the description of five new genera (Speleotes, Haliplanktos, Olisthonema, Speos, and Iphianassa) and their type species (S. anchialus, H. antonyquinny, O. eestii, S. fyssassi, I. zackieohae) representing Chroococcales, Chroococcidiopsales, Oscillatoriales, Synechococcales, and Nostocales orders, respectively. We also found unique lineages inside the genera Komarekiella, Stenomitos, Cyanocohniella, and Nodularia, describing four new species (K. chia, S. pantisii, C. hyphalmyra, N. mediterannea). We report for the first time a widespread production of HCN amongst different taxa and habitats. Epilithic lifestyle, where cyanobacteria are more vulnerable to grazers, had the largest relative frequency in HCN production. In this work, we show novel cyanobacteria diversity from various habitats, including an unexplored anchialine cave, and possible correlation of cyanobacteria chemo- with species diversity, which may have implications on strategic focusing of screening programs on underexploited taxa and/or habitats., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Cyanobacteria are photosynthetic microorganisms that are able to produce a large number of secondary metabolites. In freshwaters, under favorable conditions, they can rapidly multiply, forming blooms, and can release their toxic/bioactive metabolites in water. Among them, anabaenopeptins (APs) are a less studied class of cyclic bioactive cyanopeptides. The occurrence and structural variety of APs in cyanobacterial blooms and cultured strains from Greek freshwaters were investigated. Cyanobacterial extracts were analyzed with LC-qTRAP MS/MS using information-dependent acquisition in enhanced ion product mode in order to obtain the fragmentation mass spectra of APs. Thirteen APs were detected, and their possible structures were annotated based on the elucidation of fragmentation spectra, including three novel ones. APs were present in the majority of bloom samples (91%) collected from nine Greek lakes during different time periods. A large variety of APs was observed, with up to eight congeners co-occurring in the same sample. AP F (87%), Oscillamide Y (87%) and AP B (65%) were the most frequently detected congeners. Thirty cyanobacterial strain cultures were also analyzed. APs were only detected in one strain ( Microcystis ichtyoblabe ). The results contribute to a better understanding of APs produced by freshwater cyanobacteria and expand the range of structurally characterized APs.

Sponges form symbiotic relationships with diverse and abundant microbial communities. Cyanobacteria are among the most important members of the microbial communities that are associated with sponges. Here, we performed a genus-wide comparative genomic analysis of the newly described marine benthic cyanobacterial genus Leptothoe (Synechococcales). We obtained draft genomes from Le. kymatousa TAU-MAC 1615 and Le. spongobia TAU-MAC 1115, isolated from marine sponges. We identified five additional Leptothoe genomes, host-associated or free-living, using a phylogenomic approach, and the comparison of all genomes showed that the sponge-associated strains display features of a symbiotic lifestyle. Le. kymatousa and Le. spongobia have undergone genome reduction; they harbored considerably fewer genes encoding for (i) cofactors, vitamins, prosthetic groups, pigments, proteins, and amino acid biosynthesis; (ii) DNA repair; (iii) antioxidant enzymes; and (iv) biosynthesis of capsular and extracellular polysaccharides. They have also lost several genes related to chemotaxis and motility. Eukaryotic-like proteins, such as ankyrin repeats, playing important roles in sponge-symbiont interactions, were identified in sponge-associated Leptothoe genomes. The sponge-associated Leptothoe stains harbored biosynthetic gene clusters encoding novel natural products despite genome reduction. Comparisons of the biosynthetic capacities of Leptothoe with chemically rich cyanobacteria revealed that Leptothoe is another promising marine cyanobacterium for the biosynthesis of novel natural products.

Cyanobacteria are often reported as abundant components of the sponge microbiome; however their diversity below the phylum level is still underestimated. Aiming to broaden our knowledge of sponge-cyanobacteria association, we isolated cyanobacterial strains from Aegean Sea sponges in previous research, which revealed high degree of novel cyanobacterial diversity. Herein, we aim to further characterize sponge-associated cyanobacteria and re-evaluate their classification based on an extensive polyphasic approach, i.e. a combination of molecular, morphological and ecological data. This approach resulted in the description of five new genera (Rhodoploca, Cymatolege, Metis, Aegeococcus, and Thalassoporum) and seven new species (R. sivonenia, C. spiroidea, C. isodiametrica, M. fasciculata, A. anagnostidisi, A. thureti, T. komareki) inside the order Synechococcales, and a new pleurocapsalean species (Xenococcus spongiosum). X. spongiosum is a baeocyte-producing species that shares some morphological features with other Xenococcus species, but has distinct phylogenetic and ecological identity. Rhodoploca, Cymatolege, Metis and Thalassoporum are novel well supported linages of filamentous cyanobacteria that possess distinct characters compared to their sister taxa. Aegeococcus is a novel monophyletic linage of Synechococcus-like cyanobacteria exhibiting a unique ecology, as sponge-dweller. The considerable number of novel taxa characterized in this study highlights the importance of employing polyphasic culture-dependent approaches in order to reveal the true cyanobacterial diversity associated with sponges., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Microcystins (MCs) are cyanobacterial toxins and potent inhibitors of protein phosphatases 1 (PP1) and 2A (PP2A), which are involved in plant cytoskeleton (microtubules and F-actin) organization. Therefore, studies on the toxicity of cyanobacterial products on plant cells have so far been focused on MCs. In this study, we investigated the effects of extracts from 16 (4 MC-producing and 12 non-MC-producing) cyanobacterial strains from several habitats, on various enzymes (PP1, trypsin, elastase), on the plant cytoskeleton and H 2 O 2 levels in Oryza sativa (rice) root cells. Seedling roots were treated for various time periods (1, 12, and 24 h) with aqueous cyanobacterial extracts and underwent either immunostaining for α -tubulin or staining of F-actin with fluorescent phalloidin. 2,7-dichlorofluorescein diacetate (DCF-DA) staining was performed for H 2 O 2 imaging. The enzyme assays confirmed the bioactivity of the extracts of not only MC-rich (MC+), but also MC-devoid (MC-) extracts, which induced major time-dependent alterations on both components of the plant cytoskeleton. These findings suggest that a broad spectrum of bioactive cyanobacterial compounds, apart from MCs or other known cyanotoxins (such as cylindrospermopsin), can affect plants by disrupting the cytoskeleton.

Symbioses between sponges and photosynthetic organisms are very diverse regarding the taxonomy and biogeography of both hosts and symbionts; to date, most research has focused on the exploration of bacterial diversity. The present study aims to characterize the culturable diversity of photosynthetic eukaryotes associated with sponges in the Aegean Sea, on which no information exists. Five microalgae strains were isolated from marine sponges; the strains were characterized by morphological features, and the 18S rRNA, 18S-28S Internal Transcribed Spacer, and ribulose-bisphosphate carboxylase large chain (rbcL) sequences. Our polyphasic approach showed that the strains belonged to the green-alga Acrochaete leptochaete, the diatom Nanofrustulum cf. shiloi, the rhodophyte Acrochaetium spongicola, and the chlorachniophyte Lotharella oceanica. A. leptochaete is reported for the first time in sponges, even though green algae are known to be associated with sponges. Nanofrustulum shiloi was found in association with the sponges Agelas oroides and Chondrilla nucula, whereas information existed only for its association with the species Aplysina aerophoba. Acrochaetium spongicola was found for the first time in association with sponges in the eastern Mediterranean. Moreover, we report herein for the first time a sponge-chlorarachniophycean association. Our research revealed new diversity of microalgae associated with sponges and added new records of sponge species, previously unknown for their association with microalgae., (© 2020 International Society of Protistologists.)

The production of β-Ν-methylamino-L-alanine (BMAA) in cyanobacteria is triggered by nitrogen-starvation conditions and its biological role, albeit unknown, is associated with nitrogen assimilation. In the present study, the effect of BMAA (773 μg L -1 ) on nitrogen metabolism and physiology of the non-diazotrophic cyanobacterium and non-BMAA producer, Synechococcus sp. TAU-MAC 0499, was investigated. In order to study the combined effect of nitrogen availability and BMAA, nitrogen-starvation conditions were induced by transferring cells in nitrogen-free medium and subsequently exposing the cultures to BMAA. After short-term treatment (180 min) and in the presence of nitrogen, BMAA inhibited glutamine synthetase, which resulted in low concentration of glutamine. In the absence of nitrogen, although there was no effect on glutamine synthetase, a possible perturbation in nitrogen assimilation is reflected on the significant decrease in glutamate levels. During the long-term exposure (24-96 h), growth, photosynthetic pigments and total protein were not affected by BMAA exposure, except for an increase in protein and phycocyanin levels at 48 h in nitrogen replete conditions. Results suggest that BMAA interferes with nitrogen assimilation, in a different way, depending on the presence or absence of combined nitrogen, providing novel data on the potential biological role of BMAA., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Cyanobacteria can form extensive blooms in water with concurrent production and release of a large number of chemically diverse and bioactive metabolites, including hazardous toxins. Significant number of the metabolites belongs to non-ribosomal peptides, with unique residues, unusual structures and great potential for biotechnological application. The biosynthetic pathways of the peptides generate tens of variants, but only part of them has been identified. Microginins are an understudied class of cyanobacterial linear peptides with a characteristic decanoic acid derivative amino acid residue in their structure. In this study, cyanobacterial blooms and isolated strains from Greek lakes were analyzed for the presence of microginins by liquid chromatography coupled to hybrid triple quadrupole/linear ion trap mass spectrometer (LC-qTRAP MS/MS). Microginin structures were elucidated based on the obtained fragmentation spectra. A large number of microginins occurred in blooms of Greek freshwaters and the most frequently detected were Microginin FR1 (70% of samples), Microginin T1 (52%), Microginin 565B (52%), Microginin T2 (43%), and Microginin 565A (43%). Additionally, nine cyanobacterial strains i.e. Nostoc oryzae, Synechococcus sp., Microcystis aeruginosa, Microcystis viridis, and five Microcystis sp., were found to produce microginins. Thirty-six new microginin structures were characterized out of fifty-one totally detected variants. This is the first time that such a diversity of microginins is reported to be present in water bodies. Results clearly demonstrate the great metabolomic potential of cyanobacteria that inhabit Greek freshwaters and significantly expand the knowledge of cyanobacterial secondary metabolites with regards to the class of microginins., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Marine cyanobacteria are considered a prolific source of bioactive natural products with a range of biotechnological and pharmacological applications. However, data on the production of natural compounds from sponge-associated cyanobacteria are scarce. This study aimed to assess the potential of sponge-associated cyanobacteria strains representing different taxonomic groups for the production of bioactive compounds and the biological activity of their extracts. Phylogenetic analysis of sponge-associated cyanobacteria and screening for the presence of genes encoding non-ribosomal peptide synthetases (NRPSs) and polyketide synthases (PKSs) were performed. Methanol extracts of the sponge-associated strains were analyzed for cyanotoxin production and tested for antioxidant activity and cytotoxic activity against several human cancer cell lines and pathogenic bacteria. PKS were detected in all sponge-associated strains examined, indicating the metabolic potential of the isolates. PKS genes were more ubiquitous than NRPS genes. Cyanotoxins (i.e., cylindrospermopsin, anatoxin-a, nodularin, and microcystins) were not detected in any of the sponge-associated cyanobacterial strains. Strains belonging to Leptothoe , Pseudanabaena , and Synechococcus were found to have activity mainly against Staphylococcus aureus . In addition, sponge-associated Leptothoe strains (TAU-MAC 0915, 1015, 1115, and 1215) were found to be highly cytotoxic and in most cases more effective against human cancer cell lines than against normal cells. Extracts with the most promising bioactivity deserve further investigation in order to isolate and identify the bioactive molecule(s)., Competing Interests: The authors declare no conflicts of interest.

Background: Terrestrial, freshwater and marine green algae constitute the large and morphologically diverse phylum of Chlorophyta, which gave rise to the core chlorophytes. Chlorophyta are abundant and diverse in freshwater environments where sometimes they form nuisance blooms under eutrophication conditions. The phylogenetic relationships among core chlorophyte clades (Chlorodendrophyceae, Ulvophyceae, Trebouxiophyceae and Chlorophyceae), are of particular interest as it is a species-rich phylum with ecological importance worldwide, but are still poorly understood. In the Mediterranean ecoregion, data on molecular characterization of eukaryotic microalgae strains are limited and current knowledge is based on ecological studies of natural populations. In the present study we report the isolation and characterization of 11 green microalgae strains from Greece contributing more information for the taxonomy of Chlorophyta. The study combined morphological and molecular data., Results: Phylogenetic analysis based on 18S rRNA, internal transcribed spacer (ITS) region and the large subunit of the ribulose-bisphosphate carboxylase ( rbcL ) gene revealed eight taxa. Eleven green algae strains were classified in four orders (Sphaeropleales, Chlorellales, Chlamydomonadales and Chaetophorales) and were represented by four genera; one strain was not assigned to any genus. Most strains (six) were classified to the genus Desmodesmus , two strains to genus Chlorella , one to genus Spongiosarcinopsis and one filamentous strain to genus Uronema . One strain is placed in a separate independent branch within the Chlamydomonadales and deserves further research., Conclusions: Our study reports, for the first time, the presence of Uronema in an aquatic environment up to 40 °C and reveals new diversity within the Chlamydomonadales. The results from the ITS region and the rbcL gene corroborated those obtained from 18S rRNA without providing further information or resolving the phylogenetic relationships within certain genera, due to the limited number of ITS and rbcL sequences available. The comparison of molecular and morphological data showed that they were congruent. Cosmopolitan genera with high worldwide distribution inhabit Greek freshwaters., Competing Interests: Competing interestsThe authors declare that they have no competing interests., (© The Author(s) 2019.)

Cyanobacterial diversity associated with sponges remains underestimated, though it is of great scientific interest in order to understand the ecology and evolutionary history of the symbiotic relationships between the two groups. Of the filamentous cyanobacteria, the genus Leptolyngbya is the most frequently found in association with sponges as well as the largest and obviously polyphyletic group. In this study, five Leptolyngbya-like sponge-associated isolates were investigated using a combination of molecular, chemical, and morphological approach and revealed a novel marine genus herein designated Leptothoe gen. nov. In addition, three new species of Leptothoe, Le. sithoniana, Le. kymatousa, and Le. spongobia, are described based on a suite of distinct characters compared to other marine Leptolyngbyaceae species/strains. The three new species, hosted by four sponge species, showed different degrees of host specificity. Leptothoe sithoniana and Le. kymatousa hosted by the sponges Petrosia ficiformis and Chondrilla nucula, respectively, seem to be more specialized than Le. spongobia, which was hosted by the sponges Dysidea avara and Acanthella acuta. All three species contained nitrogen-fixing genes and may contribute to the nitrogen budget of sponges. Leptothoe spongobia TAU-MAC 1115 isolated from Acanthella acuta was shown to produce microcystin-RR indicating that microcystin production among marine cyanobacteria could be more widespread than previously determined., (© 2019 Phycological Society of America.)

Cyanobacteria are a diverse group of photosynthetic Gram-negative bacteria that produce an array of secondary compounds with selective bioactivity against a broad spectrum of organisms and cell lines. In this study, 29 strains isolated from freshwaters in Greece were classified using a polyphasic approach and assigned to Chroococcales, Synechococcales, and Nostocales, representing 11 genera and 17 taxa. There were good agreements between 16S ribosomal RNA (rRNA)- cpcBA -internal genetic spacer (IGS) characterization and morphological features, except for the Jaaginema - Limnothrix group which appears intermixed and needs further elucidation. Methanol extracts of the strains were analyzed for cyanotoxin production and tested against pathogenic bacteria species and several cancer cell lines. We report for the first time a Nostoc oryzae strain isolated from rice fields capable of producing microcystins (MCs) and a Chlorogloeopsis fritschii strain isolated from the plankton of a lake, suggesting that this species may also occur in freshwater temperate habitats. Strains with very high or identical 16S rRNA gene sequences displayed different antibacterial and cytotoxic activities. Extracts from Synechococcus cf. nidulans showed the most potent antibacterial activity against Staphylococcus aureus , whereas Jaaginema sp. strains exhibited potent cytotoxic activities against human colorectal adenocarcinoma and hepatocellular carcinoma cells. Jaaginema Thessaloniki Aristotle University Microalgae and Cyanobacteria (TAU-MAC) 0110 and 0210 strains caused pronounced changes in the actin network and triggered the formation of numerous lipid droplets in hepatocellular carcinoma and green monkey kidney cells, suggesting oxidative stress and/or mitochondrial damage leading to apoptosis.

The cyanobacterium Cylindrospermopsis raciborskii represents a challenge for researchers and it is extensively studied for its toxicity and invasive behaviour, which is presumably enhanced by global warming. Biogeography studies indicate a tropical origin for this species, with Greece considered as the expansion route of C. raciborskii in Europe. The widening of its geographic distribution and the isolation of strains showing high optimum growth temperature underline its ecological heterogeneity, suggesting the existence of different ecotypes. The dominance of species like C. raciborskii along with their ecotoxicology and potential human risk related problems, render the establishment of a clear phylogeography model essential. In the context of the present study, the characterization of Cylindrospermopsis raciborskii TAU-MAC 1414 strain, isolated from Lake Karla, with respect to its phylogeography and toxic potential, is attempted. Our research provides new insights on the origin of C. raciborskii in the Mediterranean region; C. raciborskii expanded in Mediterranean from North America, whilst the rest of the European strains may originate from Asia and Australia. Microcystin synthetase genes, phylogenetic closely related with Microcystis strains, were also present in C. raciborskii TAU-MAC 1414. We were unable to unambiguously confirm the presence of MC-LR, using LC-MS/MS. Our results are shedding light on the expansion and distribution of C. raciborskii, whilst they pose further questions on the toxic capacity of this species., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Insight into how environmental change determines the production and distribution of cyanobacterial toxins is necessary for risk assessment. Management guidelines currently focus on hepatotoxins (microcystins). Increasing attention is given to other classes, such as neurotoxins (e.g., anatoxin-a) and cytotoxins (e.g., cylindrospermopsin) due to their potency. Most studies examine the relationship between individual toxin variants and environmental factors, such as nutrients, temperature and light. In summer 2015, we collected samples across Europe to investigate the effect of nutrient and temperature gradients on the variability of toxin production at a continental scale. Direct and indirect effects of temperature were the main drivers of the spatial distribution in the toxins produced by the cyanobacterial community, the toxin concentrations and toxin quota. Generalized linear models showed that a Toxin Diversity Index (TDI) increased with latitude, while it decreased with water stability. Increases in TDI were explained through a significant increase in toxin variants such as MC-YR, anatoxin and cylindrospermopsin, accompanied by a decreasing presence of MC-LR. While global warming continues, the direct and indirect effects of increased lake temperatures will drive changes in the distribution of cyanobacterial toxins in Europe, potentially promoting selection of a few highly toxic species or strains., Competing Interests: The authors declare no conflict of interest.

Sponge-cyanobacteria associations have attracted research interest from an ecological, evolutionary and biotechnological perspective. Current knowledge is, in its majority, "hidden" in metagenomics research studying the entire microbial communities of sponges, while knowledge on these associations is totally missing for certain geographic areas. In this study, we (a) investigated the occurrence of cyanobacteria in 18 sponge species, several of which are studied for the first time for their cyanobionts, from a previously unexplored eastern Mediterranean ecoregion, the Aegean Sea, (b) isolated sponge-associated cyanobacteria, and characterized them based on a polyphasic (morphological-morphometric and molecular phylogenetic analysis) approach, and (c) conducted a meta-analysis on the global diversity of sponge species hosting cyanobacteria, as well as the diversity of cyanobacterial symbionts. Our research provided new records for nine sponge species, previously unknown for this association, while the isolated cyanobacteria were found to form novel clades within Synechococcus, Leptolyngbyaceae, Pseudanabaenaceae, and Schizotrichaceae, whose taxonomic status requires further investigation; this is the first report of a Schizotrichaceae cyanobacterium associated with sponges. The extensive evaluation of the literature along with the new data from the Aegean Sea raised the number of sponge species known for hosting cyanobacteria to 320 and showed that the cyanobacterial diversity reported from sponges is yet underestimated.

Background: The checklist of Greek Cyanobacteria was created in the framework of the Greek Taxon Information System (GTIS), an initiative of the LifeWatchGreece Research Infrastructure (ESFRI) that has resumed efforts to compile a complete checklist of species reported from Greece. This list was created from exhaustive search of the scientific literature of the last 60 years. All records of taxa known to occur in Greece were taxonomically updated., New Information: The checklist of Greek Cyanobacteria comprises 543 species, classified in 130 genera, 41 families, and 8 orders. The orders Synechococcales and Oscillatoriales have the highest number of species (158 and 153 species, respectively), whereas these two orders along with Nostocales and Chroococcales cover 93% of the known Greek cyanobacteria species. It is worth mentioning that 18 species have been initially described from Greek habitats. The marine epilithic Ammatoidea aegea described from Saronikos Gulf is considered endemic to this area. Our bibliographic review shows that Greece hosts a high diversity of cyanobacteria, suggesting that the Mediterranean area is also a hot spot for microbes.

Background: Currently, cyanobacterial diversity is examined using a polyphasic approach by assessing morphological and molecular data (Komárek 2015). However, the comparison of morphological and genetic data is sometimes hindered by the lack of cultures of several cyanobacterial morphospecies and inadequate morphological data of sequenced strains (Rajaniemi et al. 2005). Furthermore, in order to evaluate the phenotypic plasticity within defined taxa, the variability observed in cultures has to be compared to the range in natural variation (Komárek and Mareš 2012). Thus, new tools are needed to aggregate, link and process data in a meaningful way, in order to properly study and understand cyanodiversity., New Information: An online database on cyanobacteria has been created, namely the Cyanobacteria culture collection (CCC) (http://cyanobacteria.myspecies.info/) using as case studies cyanobacterial strains isolated from lakes of Greece, which are part of the AUTH culture collection (School of Biology, Aristotle University of Thessaloniki). The database hosts, for the first time, information and data such as morphology/morphometry, biogeography, phylogeny, microphotographs, distribution maps, toxicology and biochemical traits of the strains. All this data are structured managed, and presented online and are publicly accessible with a recently developed tool, namely "Scratchpads", a taxon-centric virtual research environment allowing browsing the taxonomic classification and retrieving various kinds of relevant information for each taxon.

Cyanobacterial harmful algal blooms represent one of the most conspicuous waterborne microbial hazards in aquatic environments mostly due to the production of toxic secondary metabolites, mainly microcystins (MCs). Other bioactive peptides are frequently found in cyanobacterial blooms, yet their concentration and ecological relevance is still unknown. In this paper we studied the presence and concentration of cyanobacterial peptides (microcystins, anabaenopeptins, anabaenopeptilides) in 36 Greek freshwater bodies, using HPLC-DAD, ELISA, and PP1IA. Microcystins were found in more than 90% of the samples investigated, indicating that microcystin-producing strains seem to also occur in lakes without blooms. Microcystins MC-RR, MC-LR, and MC-YR were the main toxin constituents of the bloom samples. Anabaenopeptin A and B were predominant in some samples, whereas anabaenopeptolide 90A was the only peptide found in Lake Mikri Prespa. The intracellular concentrations of anabaenopeptins produced by cyanobacterial bloom populations are determined for the first time in this study; the high (>1000 µg·L(-1)) anabaenopeptin concentration found indicates there may be some impacts, at least on the ecology and the food web structure of the aquatic ecosystems. The maximum intracellular MC values measured in Lakes Kastoria and Pamvotis, exceeding 10,000 µg·L(-1), are among the highest reported.

Cyanobacteria harmful algal blooms (or CyanoHABs) represent one of the most conspicuous waterborne microbial hazards in aquatic environments mostly due to the production of harmful secondary metabolites, known as cyanotoxins. In freshwaters of Greece only the presence of microcystins (MCs) has been reported despite the increasing occurrence of species able to produce other cyanotoxins too. In this paper, we studied the occurrence of potentially toxic cyanobacteria in water samples collected from six lakes and reservoirs in Greece. A multi-technique approach was applied by the use of microscopy, molecular, and immunological methods. Cyanobacteria were found in all the sites ranging from 4.7 × 10³ to 5.3 × 10⁸ individuals L⁻¹, representing >70% of the total phytoplankton abundance. Microcystins (MCs), cylindrospermopsins (CYNs), and saxitoxins (STXs) were detected using ELISA, in concentrations ranging from 3.9 to 108 μg L⁻¹, from 0.3 to 2.8 μg L⁻¹ and from 0.4 to 1.2 μg L⁻¹, respectively. In half of the samples examined more than one cyanotoxins were detected. Our results document the first report on the occurrence of CYN and STX in freshwaters of Greece and show that potential STX producers are Cylindrospermopsis raciborskii and Aphanizomenon flos-aquae. Further studies are needed to assess potential CYN producers. This study provides further data on the distribution and toxicity of C. raciborskii and Aph. flos-aquae and documents a C. raciborskii dominated bloom producing STX in Europe., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Microcystins (MCs) and anabaenopeptins from 26 cyanobacterial bloom samples dominated mainly by the genus Microcystis and collected from seven Greek freshwaters were identified and quantified by high-performance liquid chromatography coupled to a diode array detector. All the samples analyzed contained microcystins; in 27% of the samples anabaenopeptins were detected but not anabaenopeptilide (A). In each sample 1-7 microcystins and up to two anabaenopeptins (anabaenopeptins A and B) were identified. MC-RR and MC-LR were the predominant microcystins, followed by MC-YR. MC-LA and demethylated variants of MC-LR and MC-RR also were present but were not abundant. Total content of microcystin and anabaenopeptin varied from 40 to 2565 microg g(-1) freeze-dried material (mean 674.5 microg g(-1)) and from undetectable to 48 microg g(-1) freeze-dried material (mean 6.2 microg g(-1)), respectively. Qualitative and quantitative variation in the microcystins in the samples indicates there may be geographical trends in the distribution of microcystins. This study reports for the first time (1) the widespread occurrence of several different microcystins in Greek freshwaters and (2) quantitative data on the anabaenopeptins produced in natural cyanobacterial populations., ((c) 2005 Wiley Periodicals, Inc.)